Internet Protocol (IP) networks were originally designed to communicate packets between a host and a corresponding node (CN). A corresponding node can send data packets to the IP host by setting the destination of these packets to that of the IP host. The IP network discovers the connectivity of the network nodes and routes the data packet using standard topology discovery and IP protocols such as Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP). With the knowledge of the network and the IP forwarding mechanisms, data packets flow from the corresponding node to the IP host typically along the shortest route in the network. Current IP networks predominantly use a specific IP addressing scheme and routing protocols known as IP version 4 (IPv4).
With the development of data applications such as Voice over IP (VoIP), Short Message Service (SMS), Multi-Media Messaging Service (MMS) in mobile networks it became necessary to extend signaling and routing protocols to enable communication with mobile devices that can attach to the network from anywhere via a local access point. With that objective in mind Mobile IPv4 (MIPv4) was developed. FIG. 1 illustrates a conventional network implementing MIPv4. As illustrated in FIG. 1, a mobile device 102 (hereafter called Mobile Node (MN)) is registered with a router 104 (hereafter called Home Agent (HA)). Home agent 104 assigns a Home Address (HoA) to mobile node 102 from an IP subnetwork (“subnet”) that home agent 104 advertises into the IP network. This HoA of mobile node 102 is fixed regardless of the location of mobile node 102.
In FIG. 1 Mobile Node 1 (MN1) 102 has registered in Region 1 with its local MIP home agent. A router with which the mobile node is currently attached is called the Foreign Agent (FA), which is foreign agent 106 for MN1 102. The address of the Foreign Agent becomes the Care of Address (CoA) of mobile node 102. As illustrated in FIG. 1, in accordance with MIPv4 a MIP tunnel is established from the home agent 104 to foreign agent 106. Home agent 104 uses the MIP tunnel to forward packets to the MN1 102. Home agent 104 routes all traffic destined for MN1's 102 Home Address 1 (HoA1) through this tunnel, and foreign agent 106 at CoA1 forwards the traffic to MN1 102. For the purposes of this discussion, it is assumed that MIP Reverse Tunneling is always set to off.
MN1 102 has also completed SIP registration with SIP server 108, which has associated MN1's SIP address (steve@carrier.com) with HoA1 within the SIP infrastructure. Similarly, MN2 110 has completed MIP and SIP registration, which has established IP reachability for MN2 110 at HoA2 via CoA2 and SIP reachability at his SIP address (sid@carrier.com).
When the mobile node registers with the home agent via the foreign agent, the home agent creates a binding between the HoA and CoA and creates a tunnel for forwarding data packets addressed to HoA for the mobile node using a standard technique called IP in IP tunneling. Any corresponding node communicating with the mobile node regardless of the location of the mobile node, sends data packets to the HoA of the mobile node. Since the home agent always advertises the subnet of the mobile node, the data packets with a destination address equal to the HoA of the mobile node are always first routed to the home agent. The home agent subsequently uses the IP tunneling mechanism discussed above to forward the data packets to the CoA of the foreign agent, which then forwards the data packets to the appropriate link reaching the mobile node.
In the standard MIPv4 mechanism it is evident that the communication route for data traffic from a corresponding node to a mobile node must always pass through the home agent and then be forwarded from the home agent to the foreign agent using the current CoA associated with the mobile node. This mechanism does not allow data traffic to flow along the shortest route from the corresponding node to the mobile node. The un-optimized route for data traffic causes several deficiencies in communication quality. First, because the route may be unnecessarily long, the end-to-end transmission delay can be significantly longer than when the route does not pass through a home agent. Longer delays may cause significant quality degradation in delay-sensitive services such as VoIP and Push-to-talk over Cellular (PoC). Typically, delay in a mobile network is longer than fixed networks. Thus, additional delay may be particularly detrimental in mobile networks. Second, traffic to all the mobile nodes registered with a home agent must pass through the home agent causing congestion. In addition, a single home agent failure could unnecessarily disrupt all traffic routed through the home agent. Thus, routing performance could be degraded in the network due to the requirement that a home agent is in the forwarding path for networks using conventional MIPv4 routing. Third, more network bandwidth is required to carry traffic in a non-optimal way. More network bandwidth requirement leads to more expensive network.
Using MIPv4, mobile-to-mobile bearer traffic is forwarded through the MIP tunnels setup using MIPv4 as illustrated in FIG. 2. This ensures seamless mobility as the mobiles change their point of attachment. Specifically, the user datagram protocol (UDP) port numbers used by the real-time protocol (RTP)/UDP and real-time control protocol (RTCP)/UDP streams are negotiated and signaled by the SIP infrastructure between the mobile nodes, and the mobile nodes' HoAs are used as the IP endpoints of these streams.
The next-generation mobile IP network protocol, commonly known as IPv6, addresses this particular problem by providing a “route optimization” mode. This mode requires the mobile node to register its current binding with the corresponding node. Packets from the corresponding node are routed directly to the CoA of the mobile node. When sending a packet to the IPv6 destination of the mobile node, the corresponding node checks its bindings for an entry for the packet's destination address. If a cached binding for this destination address is found, the corresponding node uses a new type of IPv6 routing header to route the packet to the mobile node directly to the CoA indicated in this binding. Routing packets directly to the mobile node's CoA allows the shortest communications path to be used.
This method for solving the un-optimized routing problem has three fundamental drawbacks. First, MIPv6 is not ubiquitously deployed and it may take a long while to change the IPv4 and MIPv4 networks to IPv6 and MIPv6. Second, since MIPv6 is implemented in the network layer when a mobile node changes its location all the different corresponding nodes that may possibly communicate with the mobile node must be notified about the current CoA of the mobile node so that all the corresponding nodes can refresh the binding. Thus, this method may suffer from a lack of scalability with respect to mobility. Third, MIPv6 route optimization requires that all mobile nodes and corresponding nodes trust each other with respect to the exchange of bindings containing routing information. Therefore, security could pose a challenge to MIPv6 implementations.
In view of the foregoing, there is a need for a method and system for route optimization in an existing MIPv4 network without changing the IP network infrastructure, functions and protocols. Furthermore, there is a need for a system and method for route optimization in a mobile environment that is scalable and can be implemented on a peer-to-peer basis and on selected services basis.